Script Error Opens up Security Hole in Xen 3.0.3

A Red Hat update has just been released to close various vulnerabilities in the Xen virtualization solution, one of which was caused by an error in a Python script.

The vulnerability, which has been assigned the CVE number CVE-2007-4993, is in the tools/pygrub/src/GrubConf.py script and was discovered by Joris van Rantwijk. Security researchers Secunia classify the error as moderately critical. It can be exploited by manipulating the Grub bootloader. A successful attacker would have the ability to execute arbitrary commands in domain 0 which has hardware access.

Tavis Ormandy found another bug (CVE-2007-1320) which triggers a heap overflow on video-to-video copy actions in the Cirrus VGA extension. An administrative user in a guest domain might be able to exploit this to execute malicious code outside their own domain.

The third vulnerability, (CVE-2007-1321), which was also discovered by Ormandy, triggers a heap overflow in the Xen NE2000 network driver. If the driver is used, a local administrator has the ability to execute arbitrary malicious code in other domains. The developers point out that Xen does not use the buggy driver by default.

Red Hat has released an update to close all three security holes. Version 3.0.3 of Xen is affected. It is unclear whether other versions have the bugs. Xen users are advised to update their installations as quickly as possible. Red Hat is currently the only source for the updates.